Note 15 - Share-based Compensation - Valuation of Option Grants Under Stock Plans (Details)	3 Months Ended
	Jun. 30, 2020	[1]
Expected volatility	32.90%
Weighted-average volatility	32.90%
Expected dividends	4.48%
Risk-free rate	0.50%
Average risk-free rate	0.50%
Expected term (in years) (Year)	7 years 4 months 24 days
Pre-vesting executive departure rate	0.60%
Pre-vesting non-executive departure rate	2.50%

[1] Stock options were granted during the three months ended June 30, 2020. There were no stock options granted during the six months ended June 30, 2021 and the three months ended March 31, 2020.